An aircraft is propelled by a plurality of jet engines each accommodated in a nacelle that also houses a set of additional actuating devices linked to the operation thereof and providing various functions when the jet engine is operating or has stopped. These additional actuating devices particularly comprise a mechanical system for actuating thrust reversers.
A nacelle generally has a tubular structure comprising an air intake in front of the jet engine, a mid-section intended to surround a fan of the jet engine, an aft section that can house thrust reversal means and is intended to surround the combustion chamber of the jet engine, and generally ends with an ejector nozzle, the outlet of which is located downstream of the jet engine.
Modern nacelles are often intended to house a turbofan engine that can generate, via the rotating fan blades, a warm airflow (also called primary flow) coming from the jet engine combustion chamber.
A nacelle generally has an external structure, called an Outer Fixed Structure (OFS), which defines, with a concentric internal structure, called an Inner Fixed Structure (IFS), including a cowl surrounding the actual structure of the jet engine at the rear of the fan, an annular flow channel, also called a duct, the purpose of which is to channel a cold airflow, called secondary flow, which circulates outside the jet engine. The primary and secondary flows are ejected from the jet engine via the rear of the nacelle.
Each propulsion assembly of the airplane is therefore formed by a nacelle and a jet engine, and is suspended on a fixed structure of the airplane, for example under a wing or on the fuselage, via a pylon or strut attached to the jet engine or to the nacelle.
The aft section of the external structure of the nacelle is normally formed from two half-shells having a substantially semi-cylindrical shape, on either side of a longitudinal vertical plane of symmetry, and which are movably mounted such that they can be opened out between a working position and a maintenance position with a view to giving access to the jet engine.
The two half-shells are generally mounted in a pivoting manner about a longitudinal shaft forming a hinge at the upper part (at 12 o'clock) of the reverser. The half-shells are kept in the closed position by means of locks arranged along a junction line located at the lower part (at 6 o'clock).
Each half-shell is opened using at least one jack and is kept open using at least one telescopic connecting rod, said jack and said telescopic connecting rod each having a first end fastened generally on the jet engine and a second end fastened in a forward frame of said half-shell, this forward frame being the member that attaches the aft section to a fixed part of the mid-section of the nacelle.
Yet, it has been noted that a telescopic connecting rod can lose all or some of the structural and functional capacities thereof when it is subjected to the vibrations generated by the engine during a certain period of time.
It is already known to incorporate compression springs into the body of the telescopic connecting rod so as to dampen these vibrations. Nevertheless, this type of telescopic connecting rod has a certain number of disadvantages.
Firstly, the operator must exert considerable compressive forces when installing this telescopic connecting rod, which, in the end, makes the operation difficult.
Furthermore, this telescopic connecting rod must be stored in the maximum amplitude position thereof as a result of the presence of an internal compression spring, hence a loss in storage space.
Furthermore, the incorporation of a compression spring requires an enlarged diameter of the body of the telescopic connecting rod, which results in an increase in mass and size.